Hey =)
I completely played through your game and it was fun.
As some comments have already said, there are some possibilities for improvement.
Control:
I would suggest that the two upgrades be put on W + S. When playing, you usually have your fingers on the keys anyway. The control over E + R got me very confused and it did not feel smooth.
Gameplay:
The hitbox when shooting should be increased slightly. Even after the upgrade it was very hard to hit. In addition, the gems should not fall so far to the right, because you can not even hit them with the laser on the edge.
In Level 2, I often had difficulty following the gems. While this was ideal for reducing grinding, a slightly slower fall would have been desirable.
Art style:
That really touched me. I think the music does not annoy even after repeated listening.
Conclusion:
Overall, a very good game. It entertained me well and the topic is well received.
I would be very happy if you also criticized my game =)